METHOD FOR DETECTING DEFECTS IN A ROD-SHAPED TRANSPARENT OBJECT

摘要

A method for inspecting defects inside a rod-shaped transparent object by using a scanning beam of parallel light rays directed onto a rod-shaped transparent object orthogonally to the longitudinal axis of the object so that an inspection plane comprises an object's cross-section. The scanning beam is detected at an opposite side of the rod-shaped object that is interposed to intercept the parallel rays of the scanning beam. The electric output signal from the detector is processed to produce a first light intensity profile in a first scan direction, the light intensity profile comprising a shadow region delimited by first and second shadow edges, which is indicative of the outside diameter of the object across the inspection plane. The method comprises analysing the first light intensity profile to determine the presence or absence of a peak of positive intensity within the shadow region and, if an intensity peak is determined to be present, to determine the presence or absence of a region of depressed intensity within the intensity peak. If, as a result of analysing, an intensity peak within the shadow region is determined to be absent or a region of depressed intensity is determined to be present within the intensity peak, the presence of at least one structural defect within the object's cross-section is identified. In the preferred embodiments, the rod-shaped transparent object is a glass core rod for the production of a transmission optical fibre.

主权项

1. A method for inspecting defects inside a rod-shaped transparent object comprising:
generating a first scanning beam of parallel light rays sweeping an inspection plane in a first scan direction; directing the first scanning beam onto a rod-shaped transparent object having a longitudinal axis and being arranged in such a way that the inspection plane is transverse to the longitudinal axis of the object and comprises an object's cross-section; detecting the first scanning light beam at an opposite side of the rod-shaped object that is interposed to intercept the parallel rays of the scanning beam, thereby producing a first electric output signal; processing the first electric output signal to produce a first light intensity profile in the first scan direction, the light intensity profile comprising a shadow region delimited by first and second shadow edges, the width between the first and second shadow edges being indicative of the outside diameter of the object across the inspection plane; analysing the first light intensity profile to determine the presence or absence of a peak of positive intensity within the shadow region, the peak originating from deflected rays transmitted through the object and detected, and, if an intensity peak is determined to be present, to determine the presence or absence of a region of depressed intensity within the intensity peak, and if, as a result of analysing, an intensity peak within the shadow region is determined to be absent or, if an intensity peak is determined to be present, a region of depressed intensity is determined to be present within the intensity peak, identifying the presence of at least one structural defect within the object's cross-section.